Plants for washing and defiberizing fibrous material



Oct. 27, 1964 G. v. c. VAN DOOSSELAERE 3,154,464

PLANTS FOR WASHING AND DEFIBERIZING FIBROUS MATERIAL Filed June 25, 19595 Sheets-Sheet 1 //V Vf/V Taki- My V/CTOA ('d/VSfA/W" 14W owssfmmz Oct.27, 1964 G. v. c. VAN DOOSSELAERE 3,154,464

PLANTS FOR WASHING AND DEFIBERIZING FIBROUS MATERIAL Filed June 25. 19595 Sheets-Sheet 2 I, I I 84- W 50 5B O O 35 C) //V V F/V 70/? 63) V/( 7d1? 77M/7 MM 000;[44Z7?[ Arr; it

Oct. 27, 1964 G. v. c. VAN DOOSSELAERE 3,154,464

PLANTS FOR WASHING AND DEFIBERIZING FIBROUS MATERIAL Filed June 25, 19595 Sheets-Sheet 3 Oct. 27, 1964 G. v. c. VAN DOOSSELAERE 3,154,464

PLANTS FOR WASHING AND DEFIBERIZING FIBROUS MATERIAL Filed June 25. 19595 Sheets-Sheet 4 Oct. 27, 1964 G. V. C. VAN DOOSSELAERE PLANTS FORWASHING AND DEFIBERIZING FIBROUS MATERIAL Filed June 25, 1959 Fig.5.

5 Sheets-Sheet 5 57 pl V 6%) WOW mam/r w/roaassamwz nited States PatentPLANTS FOR WASHING AND DEFIBERIZING FIEROUS MATERIAL Guy Victor Constantvan Doosselaere, 8 Rue de Merode, Grimbergen, Belgium Filed June 25,1959, er. No. 822,928

Claims priority, application Belgium, Apr. 25, 1953, 406,781, Patent519,479 2 Claims. (Cl. 1 62-26) The present invention relates to ahydrokinetic apparatus for simultaneously washing and breaking upfibrous materials of animal, vegetable or mineral nature.

It also relates to the refining or hydration of slushed leather, textileor other fibers for papermaking and other purposes.

The main object of the invention is to provide an improved apparatus forcarrying out the aforesaid operations.

It consists essentially in the provision of one or more rotaryhydrokinetic hammer mills, each equipped with cooperating abrasiveparts, as will be explained hereinafter in which the materials aretreated in the presence of quantities of a liquid such as water inamounts preferably between 100 to 1000 litres of water for each kilogramof material in the dry state.

By the term hammer mill, it must be generally understood any type ofrotary mill in which the comminution of the treated material is effectedby the impact of hard moving bodies or impact members, which strike thetreated materials at very high speed and which cause them to be brokenup into their component fibers, essentially through the efiect ofmultiple hammer blows.

It includes beater cross mills, carr mills and other machines based onthe same principle of comminution through impact which are toowell-known to warrant a description.

The hammer mill with swinging hammers mounted on pivots and free toswing in planes perpendicular to the rotational axis of the shaft of themachine is the most modern form of apparatus for comminuting by impact.

FIGURE 1 illustrates diagrammatically, an example of a typical modernhammer mill with swinging hammers.

This type of machine is best suited to the object of the presentinvention and will allow the best results to be obtained, while at thesame time it is the easiest to modify to produce a hydrokinetic hammermill in accordance with the present invention.

Usually, hammer mills of the type shown in FIG. 1 are used on dry oronly slightly wet materials, without any addition of water or otherliquids.

They then have the effect of breaking, grinding crushing and pulverizingthe treated materials, whether the texture of the material being treatedis fibrous, granular or continuous.

As opposed to an ideal defiberizing action in which the individual fibreis left undamaged, the action of a hammer mill operating on a dryfibrous material, without large amounts of water will mechanicallydestroy the fibres more or less completely according to the intensity ofthe dry impact treatment.

It may be said that it is impossible to reduce a dry 3,154,464 PatentedOct. 27, 1964 material to its individual fibres in a hammer mill,without shortening and breaking these component fibers to such an extentthat they become unfit for most papermaking applications.

There are, however, instances when hammer mills have been fitted withwatertight bodies and have been used with an aqueous suspension offibrous materials, or on dry fibrous materials, which were fed into themills simultaneously with large amounts of water or other liquids, theweight of which was in the range between 10 times and times the weightof the dry materials.

In such cases, the type of action exerted by the hammer mills on thefibrous materials undergoing treatment undergoes a complete change.

Firstly the presence of large amounts of water surrounding the fibrousmaterials, and rapidly incorporated into their structure, completelydamps the impacts to which the materials are subjected. The water actsas a plasticizer both around and into the fibers, preventing the brutaland excessive comminution, bursting and cutting of the fibers whichtakes place in hammer mills when the materials are treated in the drystate.

Secondly, the hammers rotating and swinging rapidly in the liquidmedium, give rise to high speed water laminas, the directions of whichare continually changed or broken by the interactions between treatedmaterials, water, hammer tips and inside surfaces of the breakingchamber of the hammer mills.

Besides its action as a plasticiser for the fibres and its ownhydrokinetic disintegrating action under conditions of high turbulence,the water acts as an extracting medium, thereby replacing pressurizedair, which in most modern hammer mills, equipped with extractor fans, isused to help the discharge of the dry treated materials through theoutlet sieves.

Practically, using hammer mills with large amounts of water on fibrousmaterials, it becomes possible to defiberize the latter very thoroughlywith very little damage to, but good separation of, the individualfibers.

The resulting pulp has longer fibers than would be the case, had it beendefiberized by more conventional means like edge runners, beaters, etc.

Moreover, the output of the hammer mill is substantially free of bundlesand other agglomerations of fibers, and it is possible to hydrate thepulp when using such hammer mills with much less cutting, for the samedegree of hydration, than is possible when using conventional pulppreparation equipment.

However, hammer mills have never become popular for wet stockpreparation in the paper and pulp industry, and this in spite ofattempts to commercialize various types especially constructed ormodified, to work with large amounts of water.

The reason for this lack of commercial success of such hammer mills liesin the fact that their power consumption, relative to output has alwaysbeen very high, thereby more than offsetting the advantages oflered fromthe view-point of fiber quality.

According to the present invention, it is possible to defiberize and/orhydrate fibrous materials or slurries through a hammer mill, with muchhigher efiiciency, better quality of fiber output and lower powerconsump- 3 tion than was heretofore possible with either conventionalpulp preparation machines, or hammer mills modified according to theprior art.

The essential feature of the invention is that the working surfaces ofthe breaking chamber of a suitably watertight hammer mill are lined withabrasive blocks made of resin bonded, or aluminous cement bonded,Carbonlndum or Corindon blocks, whereby directional changes of the waterlaminas are caused to take place by the interaction between the tips ofthe rotating hammer, the fibrous material being treated and the roughabrasive surfaces of the lining.

The Carborundum or Corindon used for making these blocks consists of amixture of grains, the size of which ranges from number 12 to number 16.

These size numbers relate to the accepted commercial classification ofCarborundum and Corindon grains according to their average sizes.

The provision of abrasive lining blocks of suitable composition,suitably placed in the hammer mill, creates a considerably increasedhydraulic agitation, which causes defiberizing and/or hydrating actionsto take place much more rapidly than even was the case before.

An important point of the present invention is that the distance betweenthe working surfaces of the abrasive blocks and the tips of the hammers,when the latter are in their fully extended radial positions should bein the range between and 12 mm., at which distance the best output perinput horsepower for any given material is obtained from the mill.

If the surface of the abrasive blocks is closer to the hammer tips, theoutput of treated material per input horsepower applied to the mainshaftof the mill decreases rapidly.

This is of course quite contrary to what might be expected at firstsight, but it is caused by the completely novel and purely hydrokinetictype of work effected in the hammer mill by the abrasive linings of thebreaking chamber.

It is obvious that, if the action of the abrasive surfaces of the blocksor linings involved the mechanical cutting action that they normallyperform, the operational efficiency of the machine would be increased byhaving the circumferences described by the tips of the working hammersbrought as close as possible to the abrasive surfaces, or in other wordsby reducing the clearance distance between abrasive surfaces and hammertips.

This reduced clearance would increase the mechanical rubbing of thetreated pump against the abrasive surfaces and thereby enhance the speedof disintegration, if the action of the abrasive linings were a purelymechanical one.

The optimum clearance distance between abrasive linings and hammer tips,in a hammer mill working on a liquid pulp has been found experimentallyto be the unexpectedly large distance of 10 to 12 mm. which clearlyestablishes that the action of the cooperating hammer tips and abrasivelinings is purely hydraulic.

The optimum clearance is consequently that distance where theinteractions between the tips of the rotating hammers, the fibrousmaterials being treated and the rough abrasive surfaces of the lining,cause the maximum amount of directional changes or turbulence of thewater laminas totake place.

The function of the rough surfaces of the abrasive linings thus consistsexclusively in increasing the hydraulic turbulence or violent agitationin the working chamber of the hammer mill.

When a hammer mill, rendered watertight, is equipped with abrasiveblocksof a suitable nature and grain, located to provide an optimum clearancedistance from the circumference described by the tips of the rotorhammers, it is still possible to improve its efiiciency by the followmgarrangement.

The sieve of the hammer mill is divided into two parts one of which hasperforations of a larger diameter than the other.

Each part of the sieve communicates separately with an individualdischarge outlet from the mill.

The pulp coming out of the outlet which corresponds with the largerperforations is continuously recycled into the mill by means of a pumpof any suitable type.

This recycling causes an increase in the output of usable pulp per inputhorsepower applied to the mill shaft which according to the type of pulpbeing treated, may amount to from 10 to 50%, as compared with the pulpoutput of the same mill, operating on the same pulp without recycling.

This may be explained by the fact that, while on the one hand thepulping water and the completely separated fibers will flow easilythrough the perforations of a sieve suited to the type of materialtreated, the yet unseparated bundles of fibers or partially defiberizedpieces of material being treated will not pass through the smaller holesbut will pass through the larger holes and be subjected to furthertreatment.

The accumulation of partially treated material on the inside surface ofthe sieve, which would exert a powerful mechanical braking action on thehammer tips and correspondingly higher power consumption is herebyavoided.

If the sieve is previously provided with a section or zone where theperforations are larger, the partially defiberized and undefiberizedparts of the stock, instead of rotating in the mill as a very muchthickened pulp and braking the hammers, will pass through the largeperforations, and be recycled inside the mill mixed with the rest of thefresh supply of incoming pulp. The recycled material will theneventually be defiberized by the hydrokinetic agitation, with low powerconsumption instead of by a mechanical impact and rubbing action whichwould require a higher input power.

Besides the points already covered, it is important to note that theangular speed of the beating rotor of a hammer mill constructed inaccordance with the present invention, should preferably be kept at orabove 3,000 revolutions per minute.

The annexed drawings show several illustrative embodiments of theinvention given only by way of examples:

FIGURE 1 is a diagrammatic vertical section through a typical modernhammer mill with swinging hammers as built for dry operation.

FIGURE 2 shows a transverse vertical cross section through the samehammer mill, as modified in accordance with the present invention.

FIGURE 3 shows an axial vertical cross-section through the same hammermill.

FIGURE 4 shows an embodiment suited to the defiberizing of dry materialswhich are fed into the mill in dry form while water is fed into itsimultaneously.

FIGURE 5 shows an embodiment suited to the treatment of slushed pulp ormaterials already suspended in water.

FIGURE 6 is a flow sheet diagram of a plant as used for defiberizing andwashing rags, ropes or other strong fibrous materials.

FIGURES 7 to 9, inclusive, are schematic showings of variousapplications of the invention.

Referring to FIG. 1, there is shown a conventional hammer millcomprising a breaking chamber 1 provided with metallic elements 2 whichconstitute the inner linings or working surfaces of the breaking chamberand which may be serrated as shown. An inlet or delivery chute 3 for theincoming material to be treated communicates with the upper portion ofthe breaking chamber 1. Centrally disposed in the breaking chamber 1 isa hammer bearing rotor 4 which is rotatably mounted on a power drivenshaft 5. The rotor 4 carries a plurality of outwardly extending hammermembers 6 each of which is individually pivoted to the rotor 4 at 7. Atthe bottom of the breaking chamber 1, there is provided asemicylindrical screening member 8 through which the treated material isdelivered to a discharge duct 9. The treated material travels in thedirection of the arrow 10 under the influence of suction provided by anextractor fan or blower 11.

As shown in FIGS. 2 and 3 and in accordance with the present invention,the conventional hammer mill of FIG. 1 is modified to such extent as maybe required so that it is Water-tight instead of merely relativelyairtight, the water tight housing being designated 20. The water tighthousing 2% defines a water tight breaking chamber 21. The upper portionof the water tight breaking chamber 21 is lined with the abrasive blocks22, the grains of which range in size from number 12 to number 16. Theabrasive linings 22 replace the usual metallic linings 2 shown in FIG.1.

Centrally disposed in the water tight breaking chamber 21, is ahammer-bearing rotor 23 which is shown keyed on a power driven rotatableshaft 24. The rotor 23 rotates clockwise as viewed in FIG. 2 and carriesa plurality of outwardly extending hammer members 25 each of which isindividually pivoted to the rotor 23 at 26.

The sieve or perforated plate, through which the stock is forced by thecentrifugal action of the rotor, is divided into two sections. A firstsection 27 communicates with discharge outlet 28, and a second section29 communicates with discharge outlet 30.

To prevent the stock to be recycled which passes through section 29 ofthe sieve and flows into outlet 3 from mixing with the finished stockpassing through section 27 of the sieve into outlet 28, provision ismade of a rubber sealing member 31, held by shaft 32, which can berotated to free the sieve when it is necessary to remove or replace thelatter.

This sealing member 31 is pressed against the sieve throughout theentire Width of the latter. It is also pressed against the beak-shapedportion 33 of the base 34 of the machine.

The stock to be recycled which passes through section 29 of the sievewill thus flow over the assembly of pieces 31 and 32, into outlet 3%,from where it can be fed into a pump and recycled into the input of themachine. Both the incoming untreated stock and the recycled pulp are fedinto the mill through inlet 35.

Reverting to the abrasive linings, it has been found convenient andpractical to make them out of a number of separate quadrangular abrasiveblocks 22 connected to the walls 36 and 37 of the treating chamber 21 bybolts 38, Washers or shims 39 being provided to ensure that the workingsurfaces 36 of the abrasive blocks 22 are set at the proper clearancedistance from the tips of hammers 25 when these are in the fullyextended radial position as shown in FIGURE 2.

In the embodiment shown in FIG. 4, water is supplied by an inlet pipe 44arranged at the upper end of a watertight funnel 41. The upper end offunnel 41 communicates with a horizontal duct 42 through which thefibrous material to be treated is supplied in a dry or semi-dry state.The lower end of funnel 41 communicates with the upper portion of thewatertight breaking chamber 21 through an inclined watertight chute 43.

No blower, fan or similar device is provided; the stock forced by thecentrifugal force through sections 27 and 29 of the sieve being throwninto outlets 28 and 3t] and from there by gravity into chests 44 and 45respectively.

Chest 44 contains completely defiberized and/or refined finished stockwhile the incompletely finished stock going into the small intermediatechest 45 is constantly recycled into inlet funnel 41 through pump 46 andpipe 47.

FIG. 5 shows a modified form of the invention for use with slushed orsemi-slushed stocks. The inlet duct comprises an inclined portion 48through which the slushed or semi-slushed stock is delivered to thewatertight breaking chamber 21. Additional water if necessary, isdelivered through a water supply duct 49 which merges tangentially withthe stock supply duct 48 at 50. The apparatus of FIG. 5 is otherwisesimilar to that of FIG. 4 described above.

The flow sheet of FIG. 6 illustratively shows an example of a plantadapted to be used for the washing and defiberizing of, for instance,rags.

The textile waste conveyed to entry 48 is cut by a ragcutter 49,according to the usual practice; it is then roughly shredded in a drycondition, either in a disk mill or in a hammer mill 5t fitted with anoutlet sieve having round perforations of between and 4-0 mm. diameter.

After having been shredded, the rags are ready for the principaldefiberizing and washing treatment.

To that end, in the example shown, the roughly shredded rags areconveyed by the blower 51 of the hammer mill to a watertight hammer mill52, which is of the general type shown in FIGS. 4 and 5, and to whichpulping Water is supplied by a pipe 53.

This watertight hammer mill 52 discharges the finished treated pulp intoa thickener 54 of any suitable type which thickens the pulp to asuitable consistency for storage and which at the same time extracts thedirt and impurities which are dispersed or dissolved in the dilutionWater.

While the finished material flows or falls from the thickener 54- into astock chest 55, for instance, the dilution water used for defiberizingand washing the stock in the watertight hammer mill 52 may be recycledto be used again.

For this purpose, a pump 56 pumps the water up to a water storage tank57, which is fitted to an overflow pipe 58 for the outlet of the surplusdirt bearing water and with a fresh Water inlet pipe 59. A pipe 60connected to pipe 53 brings the pulping water from the tank 57 to thewatertight hammer mill 52.

The partially finished material flowing out of the section of the sieveof hammer mill 52 equipped with the larger perforations flows throughpipe or duct e1 into recycling chest 62 from where it is recycled bypump 63 through pipe 64 into the inlet of mill 52, when it combines withthe incoming shredded rags and pulping water.

Other combinations of elements may be utilized comprising several hammermills arranged either in parallel or preferably in series to provideconsecutive treatments.

For instance, one or several hammer mills can be placed after thethickener 54- to perform an extra Washing and pulping action or toachieve other results which are later described.

The flow sheet of FIGURE 7 illustratively shows an example of a plantadapted to be used for the defiberizing of hard leather scrap.

The leather scrap, roughly precut, is conveyed from the hopper 65through the screw conveyor 66 into a hammer mill 67 in accordance withthe invention.

Water is fed into the mill from pipe 68.

The finished pulp discharged through the finer perforations of the sievefalls into pipe 69 and the partially finished pulp discharged throughthe larger perforations falls into pipe 70.

The rest of the plant is clearly described by FIGURE 7, with thearrangement of the two hammer mills 71 and 74 according to theinvention, placed one after the other, both of them being seriallyconnected after the first hammer mill 69. The recycling arrangementthrough pipes 70, 72 and 75 into the recycling chest 77 and from there,through the pump 78 and the pipe 79 back into the first hammer mill 67,is also clearly shown.

The completely defiberized pulp falls into the chest 76.

At this point it may be desirable to set forth dimensional informationwhich will help to understand the application of the hammer millsaccording to the present invention.

(1) Outlet Sieves If only one hammer mill in accordance with the presentinvention is used for a defiberizing operation, the perforated steelplates which are used as outlet sieves will have circular perforations,the diameter of which may vary between 1 and 20 mm. according to theresults desired and the type of materials treated.

For instance:

For complete defiberization of sulphite pulp, smaller holes of 1 to 2mm. diameter, larger or recycling holes of 3 to 4 mm. diameter.

The same for well cooked chemical straw pulp. For thorough separation ofchrysotile asbestos fiber, smaller holes of 3 to 6 mm., with recyclingholes of 7 to 8 mm.

For defiberizing and washing cooked rope stock, smaller holes of 3 to 4mm., with recycling holes of 6 to 7 If several hammer mills are used ina sequence, the diameter of the perforations will decrease from thefirst to the last mill.

For instance, in a three stage arrangement as shown in FIGS. 7 and 8:

For uncooked and roughly preshredded textile Waste, smaller holes of 20,1 and 8 mm. with recycling holes of 30, 20 and 14 mm. respectively. Forroughly precut hard leather scrap in order to obtain a completelydefiberized pulp, smaller holes of 5, 4 and 3 mm., with recycling holesof 6, and 4 mm. respectively.

The number and arrangement of hammer mills and the mesh of the sieveswill of course be determined experimentally in accordance with thenature of the materials to be treated and the results desired concerningquality, output, etc.

(2) Power Consumption The power consumption may vary, according to thenature of the treated materials, to the previous treatment to which theyhave been subjected, and to the results desired from the impacttreatment from 0.03 to 0.3 input horsepower per kg./hour of dry materialfed into each hammer mill.

(3) Water Consumption For a rag defiberizing and washing installation,the consumption of fresh water may vary between and 50 litres per kg. ofdry pulp discharged.

It is possible, by using some of the usual water purification units,which are now used by most paper mills (save-ails, rotary vacuumfilters, etc.) to reduce fresh water consumption to a minor fraction ofthe aforesaid figures.

In addition to the advantages already mentioned and which are obtainedgenerally for all fibrous materials, the method makes it possible, inthe special case of cellulose fibres, and especially of textile fibres,to obtain a perfectly washed and defiberized half stuff, which combineshigh fibre length and good dewatering properties with some of thequalities of a hydrated pulp.

For instance, sheets made of rag half stuff, defiberized in accordancewith this method, and without any subsequent beating show exceptionalbreaking length, tear, burst resistance, and rattle. These desirableproperties, in the case of rags defiberized by conventional means, areobtained only after relatively long beating times.

This is due to the fact, that although the work of hammer millsembodying the invention does not shorten the fibres to any significantextent, the latter can be considerably bruised and fibrillatedlengthwise, if the treatment is sufficiently intense.

To summarize, the hydrokinetic hammer mill of the present inventionmakes it possible to prepare a perfectly defiberized and absolutelyclean pulp which possesses unusually good mechanical properties, whil atthe same time effecting important economies of time, power and waterconsumption, even though starting the operation with relatively impureraw materials.

The method can be employed not only for defiberizing and preparinghalf-stuffs but also for hydrating stocks which have already undergone adefiberizing treatment.

The following results, which are typical, have been observed in thecourse of strictly controlled tests.

A cotton rag pulp defiberized by a conventional method in a breakerheater, and a pulp made from absolutely identical raw materials andbrought to the same degree of disintegration by the method of thepresent hydro kinetic hammer mill have both been submitted to a heatingtreatment under the same controlled conditions, in a Banning and Seyboldprecision test beater.

The specific power consumption in the breaker beater was of 0.5 inputhorsepower per kg. of rags, while it was only of 0.42 horsepower per kg.of rags by the method used in accordance with the invention.

The following table gives the results of comparative measurementseifected on both pulps after identical beating treatments.

Pulp made from same uncooked rags but having been hammer milled twiceaccording to invention once through sieve with 10 mm. perforations, thesecond time through sieve with 4 mm. perforations. Consistency: 2% foreach pass.

Beating Time Pulp made from uncooked rags according to conventionalmethod Schopper-Riegler Schopper-Ricgler It must be noticed that, beforeany beating, pulp B had a Schopper-Riegler wetness number of 25, higherthan that of pulp A after a 60 second beating cycle.

Other tests have proved conclusively, that for a given S.R. wetnessnumber, a cellulose pulp defiberized or refined by the method and in theapparatus which embodies the subject matter of the invention, hassuperior mechanical properties to an identical pulp treated byconventional means.

It is possible widely to vary the type of refining performed by theapparatus herein described.

One may simply effect a separating and dispersing action in the fibroussuspension, or, alternatively a very high degree of hydration can beobtained, if so desired.

All other factors being unchanged, the degree of hydration will bedetermined by the working consistency.

To refine with a separating and dispersing action on the fibres and toeliminate nodules with very little hydration, the pulp should be treatedat a consistency preferably lower than 1% On the contrary, if the resultto be obtained is not only a full separation and dispersion of theindividual fibres, but also a degree of hydration, the pulp should beworked at consistencies in the range from 1% to 5% according to theultimate hydration desired.

Further data relating to prolonged and extensive tests on thedefiberizing of leather scrap will better illustrate the superiority ofthe apparatus according to the present invention.

To prepare leatherboard pulp in a leatherboard mill, four differentmethods have been used, each of them being applied for periods ofseveral months.

Firstly, a plant was used according to FIGURE 8.

Sole leather scrap, roughly cut in a rotary rag cutter 80, was fed fromthe hopper 81, through the screw conveyor 82, into a series of threerotary disc mills 83, 84 and 85 especially built and equipped forleather defiberizing.

The defiberized stock fell by gravity from the last mill 35 into thechest 86.

The mills were of the type illustrated by FIGURE 9, which is too wellknown to require detailed description.

Water is fed through pipe 87, simultaneously with the leather scrap intothe inlet 88. The leather is defiberized between the fixed toothed disc89 and the rotating disc 90, which latter disc is rotated at about 800rpm. by the vertical shaft 91. The pulp leather is thrown by centrifugalforce from between the discs into the outlet chamber 92 and the pulpthen flows out of the mill through the outlet 93.

In the plant according to FIGURE 8, all three mills were equipped withelectric motors of 100 metric horsepower each.

The first mill 83 had rough-toothed steel discs, the second mill 84- hadfine-toothed steel discs and the third mill 85 had special discs made ofCarborundum abrasive. This arrangement is quite conventional and isgenerally used for leather defiberizing. After having been used day andnight for several months, this arrangement hereinafter referred to asarrangement A was modified in the following manner.

The rotary disc mills 83, 84 and 85 were replaced by hammer millsespecially modified to make them Watertight and equipped with sieveswith round perforations of 6, 4- and 3 mm. respectively.

These hammer mills the rotors of which were rotated at 3,000 revolutionsper minute, were actuated by motors of 100 metric horsepower each.

These hammer mills were of the type illustrated at FIGURE 1, but werenot equipped with extracting fans, the watery fibrous suspension fallingby gravity from one mill into the following one.

This arrangement of hammer mills will hereinafter be referred to asarrangement B.

It was later modified according to the present invention, the metallinings 2 of breaking chamber 1 being replaced by abrasive blocks 22arranged in the manner illustrated by FIGURE 2.

The grain size of these abrasive blocks was comprised between No. 12 andNo. 16 according to the present invention, and the clearance distancebetween the working surfaces of these blocks and the hammer tips was setbetween and 12 mm.

All the other elements of arrangements A and B that is to say rag cutter80, hopper 81, conveyor 82 and chest 86 were unchanged. The same sieveswere used as in arrangement B. This third arrangement will hereinafterbe called arrangement C.

After having been in use for about six months, arrangement C wasmodified by fitting the hammer mills with twin outlets, as per FIGURE 2,dividing each of the sieves into two sections, one with small holes andthe second one with larger holes. A recycling system was installed.

The arrangement was then exactly as per FIGURE 7. The same rag-cutterwas kept as in arrangements A, B and C. The motors were still the same100 horsepower electric motors. The hopper and screw feeding systemremained the same. The diameters of the perforations were as follows.

First hammer mill according to invention: small holes 6 mm., large holes8 mm.,

Second hammer mill according to invention: small holes 4 mm., largeholes 6 mm.,

Third hammer mill according to invention: small holes 3 mm., large holes4 mm.

This last arrangement will hereinafter be called arrangement D.

'10 The following table gives the specific outputs of the fourarrangements on sole leather scrap.

Arrangement A Arrangement 13 Arrangement 0 Arrangement D 1 HP. perkg. 1. 2 H.P. per 0. 9 11.1. per 0.7 HP. per

of leather kg. of leather kg. of leather kg. of leather scrap. scrap.scrap. scrap.

Tests were made daily on the pulp obtained from each of the fourarrangements. The following table shows the average results of thesetests.

These figures show clearly the advantages derived from the presentinvention.

The largely superior fiber length obtained from arrangements C and Dshow the novel and purely hydrokinetic action of the abrasive linings,as opposed to the mechanical cutting action of the abrasive discs inarrangement A.

The lack of mechanical action of the abrasive blocks being proved by thesuperior fiber lengths in arrangements C and D, the higher specificoutput per input horsepower of arrangement C, as compared witharrangement B, can only be explained by the considerable increase inhydraulic turbulence caused by the abrasive linings in their novelfunctions.

What I claim is:

l. A plant for defiberizing, washing and improving fibrous material,especially raw material for papermaking, comprising in combination: awatertight breaking chamber of the hammer-mill type, said chamber havingan inlet portion, a rotor in said breaking chamber, hammers pivotallymounted on said rotor for swinging in planes perpendicular to the axisof said rotor, means to introduce material to be treated and largequantities of Water into said breaking chamber, a lining of abrasivematerial in at least a portion of said breaking chamber, means arrangedat the lower portion of said breaking chamber to discharge materialsubjected to the combined action of shocks produced by said hammers andhydrokinetic action produced by the abrasive lining and the water, asieve arranged to receive material from said last-named means, saidsieve having an area of relatively large perforations and an area ofrelatively small perforations, and means for collecting andrecirculating material discharge through said area of large perforationsback to said inlet portion of said chamber.

2. A plant for defiberizing, washing and improving fibrous material,especially raw material for papermaking, comprising in combination: aWatertight breaking chamber of the hammer-mill type, said chamber havingan inlet portion, a rotor in said breaking chamber, hammers pivotallymounted on said rotor for swinging in planes perpendicular to the axisof said rotor, means to introduce material to be treated and largequantities of water into said breaking chamber, a lining of abrasivematerial in at least a portion of said breaking chamber, means arrangedat the lower portion of said breaking chamber to discharge materialsubjected to the combined action of shocks produced by said hammers andhydrokinetic action produced by the abrasive lining and the water,selective means disposed to receive material from said last-named means,said selective means collecting material which exceeds predetermineddimensional limitations and discharging all other material, and meansfor recirculating material collected by said selective means back tosaid inlet portion of said chamber.

(References on following page) References Cited by the Examiner UNITEDSTATES PATENTS Winestock 1 62-26 Alfred 241-88 Miliington 162-55 Doyle241-27 Banner.

Mansfied 241-21 Hartshorn 241-8 8 Sayre.

Care 241-5 1 Klagsbrunn 241-88 Messing 162-23 6 9/55 Wandel 241-114 6/57Sanford 241-80 10/57 Maltenfort 241-88 2/58 Olive 241-88 FOREIGN PATENTS6/ 45 Great Britain.

OTHER REFERENCES Casey: Pulp and Paper, vol I, pub. by IntersciencePub., N.Y., 1952, p. 182.

DONALL H. SYLVESTER, Primary Examiner. RICHARD D. NEVIUS, MORRIS O.WOLK, Examiners.

2. A PLANT FOR DEFIBERIZING, WASHING AND IMPROVING FIBROUS MATERIAL,ESPECIALLY RAW MATERIAL FOR PAPERMAKING. COMPRISING IN COMBINATION: AWATERTIGHT BREAKING CHAMBER OF THE HAMMER-MILL TYPE, SAID CHAMBER HAVINGAN INLET PORTION, A ROTOR IN SAID BREAKING CHAMBER, HAMMERS PIVOTALLYMOUNTED ON SAID ROTOR FOR SWINGING IN PLANES PERPENDICULAR TO THE AXISOF SAID ROTOR, MEANS TO INTRODUCE MATERIAL TO BE TREATED AND LARGEQUANTITIES OF WATER INTO SAID BREAKING CHAMBER, A LINING OF ABRASIVEMATERIAL IN AT LEAST A PORTION OF SAID BREAKING CHAMBER, MEANS ARRANGEDAT THE LOWER PORTION OF SAID BREAKING CHAMBER TO DISCHARGE MATERIALSUBJECTED TO THE COMBINED ACTION OF SHOCKS PRODUCED BY SAID HAMMERS ANDHYDROKINETIC ACTION PRODUCED BY THE ABRASIVE LINING AND THE WATER,SELECTIVE MEANS DISPOSED TO RECEIVE MATERIAL FROM SAID LAST-NAMED MEANS,SAID SELECTIVE MEANS COLLECTING MATERIAL WHICH EXCEEDS PREDETERMINEDDIMENSIONAL LIMITATIONS AND DISCHARGING ALL OTHER MATERIAL, AND MEANSFOR RECIRCULATING MATERIAL COLLECTED BY SAID SELECTIVE MEANS BACK TOSAID INLET PORTION OF SAID CHAMBER.